1. The Field of the Invention
The present invention relates to a circuit for separating clock and data pulses contained in a pulse train and more particularly to a circuit which separates clock and data pulses independent of time values or frequency over a design range of about 40 to 1.
2. The Prior Art
The purpose of the present circuit is to provide an economical technique for performing a self-clocking function over a wide frequency range. The subject circuit is intended for use in magnetic recording play-back detection, however, the circuit could find application wherever fixed duty cycle pulses are required. Previously it was necessary to provide sample and hold circuits in order to attain a self-clocking function. The subject invention obviates this requirement by employing only bipolar transistors.
The input to the circuit is a train of relatively narrow pulses separated by 2 to 1 time relationships. An object of the circuit is to be independent of the time values or frequency over a design range of about 40 to 1. The circuit distinguishes a 2 to 1 ratio as long as the input frequency does not change rapidly.
The input pulse train is the result of conventional signal processing techniques performed on a real head signal in a magnetic recording application. The information encoding technique may be called F/2F, Aiken, two frequency coherent phase or phase-Manchester recording where the definition of binary 1's and 0's simply differ. A preamble of F rather than 2F frequency is written before any data in order to synchronize the self-clocking circuit.